1. Field of the Invention
The present invention relates to a data imprinting apparatus for a camera used for transferring a data pattern formed on a liquid crystal panel to photographic film. More particularly, the present invention relates to a data imprinting apparatus for a camera whereby a clear data image can be imprinted on film when the path length from the data imprinting light source to the liquid crystal panel is short, and when the diffusion angle is wide.
2. Description of the Related Art
The typical structure of a data imprinting apparatus for imprinting date information and other data to photographic film inside a camera is shown in FIG. 7. As shown in FIG. 7, this data imprinting apparatus 100 for a camera is disposed inside the camera in a space between a back cover 101 on the camera body and a pressure plate 102 disposed substantially parallel to the back cover 101 on the inside of the camera. The film 103 travels through a film path disposed on the side of the pressure plate 102 opposite that facing the back cover 101. The date, time, or other information is imprinted on the film 103 through an opening 102a in pressure plate 102.
The data imprinting apparatus 100 comprises a circuit board 114 on which an IC chip 113 is mounted, a liquid crystal display (LCD) 115 for monitoring the imprinted data, and a liquid crystal display (LCD) 116 for imprinting data, each disposed between a first frame 111 and a second frame 112. The frames 111 and 112 are fastened together by passing plural pins 112a formed on one side of the second frame 112 through matching plural holes 111a formed on one side of the first frame 111, and then crimping the heads of the pins 112a.
Various data is displayed for the operator on the monitor LCD 115. The monitor LCD 115 is fastened to the inside face of the second frame 112. The exposed surface of the monitor LCD 115 is protected by a glass cover 121 attached to second frame 112 with the surface of glass cover 121 exposed to the outside through opening 101a in back cover 101. The imprinting LCD 116 is mounted on the inside surface of the first frame 111 at a position opposing opening 102a in pressure plate 102.
IC chip 113 mounted on circuit board 114 is covered and protected by a molding 122. A signal such as a drive signal is supplied from circuit board 114 to monitor LCD 115 through a flexible connector 123. The flexible connector 123 also functions as a support plate that presses against the back, i.e., the inside surface, of the monitor LCD 115 and holds monitor LCD 115 against second frame 112. A spacer 124 prevents flexible connector 123 from tilting over, and prevents monitor LCD 115 from tilting in.
The imprinting LCD 116 positioned on the opposite side of circuit board 114 is similarly electrically connected to circuit board 114 by a pair of right and left connectors 125 and 126, which press and hold imprinting LCD 116 against first frame 111.
A data imprinting apparatus 100 thus comprised is fastened inside the camera body by mounting plate 127.
A typical optical imprinting system using imprinting LCD 116 is shown in FIGS. 8A and 8B. The components of this optical system are built in to the data imprinting apparatus 100. The imprinting LCD 116 comprises a liquid crystal panel 201 including a liquid crystal material sealed between a pair of electrode plates in a construction whereby the data pattern to be imprinted on the photographic film 103 can be formed as a light transmitting part of the panel. The emitted light from a light source lamp 202 is guided to the liquid crystal panel 201 by a reflecting mirror 203. The liquid crystal panel 201 blocks any extra light that is not part of the data pattern, and passes the remaining light to the photographic film 103 as the data pattern. As a result, a data image corresponding to the data pattern is imprinted on photographic film 103.
However, liquid crystal panel 201 alone is not sufficient to block all extraneous light, and the contour of the data image imprinted on the photographic film 103 through the light transmitting part of the liquid crystal panel 201 is not sharp if only liquid crystal panel 201 is used as a light shield. To avoid this problem, a light mask 206 for blocking light has conventionally been disposed between the light source lamp 202 and liquid crystal panel 201.
As shown in FIG. 8B, light mask 206 disposed for this purpose comprises a light mask surface 210 including a light transmitting part 208 and a light shield part 209 in the area outside the light transmitting part. The light transmitting part 208 is defined by plural light transmitting segments 208a, which are formed in an area and shape corresponding to and overlaying the segments 207 of the liquid crystal panel 201 in which the data pattern is formed. As a result, extraneous light is blocked from the light emitted to the liquid crystal panel 201 by this light mask 206.
It should be noted that the light mask 206 is typically made by forming a metallic film in a particular pattern on a glass substrate by means of plating, vapor deposition, or other film formation technique, leaving the areas in which the metallic film is not formed as light transmitting part 208.
As will be evident from the above description, extraneous light is removed from the light incident to the liquid crystal panel 201 by the disposition of light mask 206 in a data imprinting apparatus for a camera constructed as described above. However, light passing through liquid crystal panel 201 also diffuses upon passage. As a result, the loss of data image sharpness resulting from this diffusion is not completely prevented. One possible method of avoiding this problem is to place the light mask 206 on the side of the liquid crystal panel 201 from which light is emitted (the light emission side).
As shown in FIG. 9A, another method of avoiding this problem, as proposed by the inventor is attaching polarizing plates 211 and 212 each on a side of the two glass electrode panels 201a and 201b, respectively, comprising liquid crystal panel 201, and then attaching a shield mask 213 on the surface of the polarizing plate 211 on the light emission side. A loss of sharpness in the data image resulting from diffusion of light passing liquid crystal panel 201 can be prevented by thus disposing shield mask 213 on the light emission side of the liquid crystal panel 201.
While such parameters as the path length from the data imprinting light source to the liquid crystal panel and the diffusion angle of emitted light are generally constant in this type of data imprinting apparatus for a camera, it is necessary to further shorten the path length, for example, to achieve a smaller, more compact data imprinting apparatus. If the length of the data pattern that can be imprinted on film is constant, shortening the path length necessarily increases the diffusion angle of the emitted light. As a result, sharpness of the data image at both ends of the imprinted data pattern can be lost. The reason for this loss of sharpness is described below.
As shown in FIG. 9A, the diffusion angle .0. of the light emitted from light source lamp 202 and incident on liquid crystal panel 201 increases with the distance from the optical axis L1 of the emitted light; as measured on the perpendicular. The diffusion angle of light emitted to the segments of the liquid crystal panel 201 corresponding to the end areas of the imprintable data pattern 220 is therefore greater than the diffusion angle of segments nearer the optical axis.
FIG. 9B is an enlarged view of the area of the dotted circle in FIG. 9A, i.e., the area at one end of data pattern 220. Plural segments that can be switched between light transmitting and non-transmitting states are formed in liquid crystal panel 201 in a liquid crystal layer 201c sealed between a pair of glass electrode plates 201a and 201b as shown in FIG. 9A. It is assumed in the following explanation that segment 230 is a segment at the farthest outside edge of the imprintable data pattern. The transmission width of segment 230 is indicated by two dotted lines in FIG. 9B. If the refractive index of the liquid crystal panel components is ignored, light transmitted by segment 230 passes at the diffusion angle .0. of the emitted light.
Light transmitting segment 208a is formed on the light mask surface 210 of light mask 206 in a plane perpendicular to the optical axis L1 at a position corresponding to segment 230 in the liquid crystal panel. In general, the width of a segment 230 formed on the liquid crystal panel by a liquid crystal panel electrode pattern, which can be switched between light transmitting and non-transmitting states, is greater than the width of a light transmitting segment 208a on the light mask side, and the widthwise center positions of light transmitting segment 208a on the light mask side and a corresponding segment 230 on the liquid crystal panel side are aligned, i.e. coplanar in a plane parallel to the optical axis L1.
As a result, when light transmitted through segment 230, switched to a light transmitting state, on the liquid crystal panel side diffuses at a constant diffusion angle .0. and reaches light mask surface 210 of light mask 206, an illumination area 240 is formed offset, on a perpendicular to the optical axis L, from light transmitting segment 208a on the light mask side. This does not create a problem if the entire transmitted light segment 230 on the light mask side is contained within illumination area 240. However, if the diffusion angle .0. is great and the electrode plates of the liquid crystal panels that are used are thick, illumination area 240 may be formed at a position not completely covering light transmitting segment 230.
If part of illumination area 240 is removed from light transmitting segment 230, part of the light passing through segment 230 on the liquid crystal panel side will be blocked by the shield part of the light mask as shown by the diagonal dotted line in FIG. 9B. This blocked light is indicated as light 250. As shown in FIG. 9C this results in partial dropout of the transmitted light pattern, which corresponds to the data pattern to be imprinted on the photographic film. This dropout thus prevents formation of a complete, sharp data image.
While the greatest potential for partial dropout of the light transmitted for data imprinting is at both ends of the data pattern, dropout can also occur in other parts of the data pattern. This is because the illuminated area formed on the light mask surface by light transmitted through a segment on the liquid crystal panel side shifts in a direction increasing in distance from the optical axis L1 as shown in FIG. 10. The light transmitting segments of the light mask are indicated by a solid line in FIG. 10, the area of the corresponding segment on the liquid crystal panel is indicated by a dot-dot-dash line, and the illuminated area formed on the light mask by light transmitted through a corresponding segment on the liquid crystal panel is indicated by a dotted line.
It is significant to note that the effect of this offset from the optical axis in the formation of an illuminated area on the light mask by light transmitted by a segment of the liquid crystal panel has not been previously addressed, and there are no proposals for a solution to this problem in the literature.